Existing in-vitro tumor drug delivery models are often poor predictors of drug delivery to tumors. Simple in-vitro models cannot accurately capture complex phenomenon involved in tumor drug delivery, which are affected by the physico-chemical properties drugs and delivery vehicles and complex tumor microvasculature. Tumor microvasculature is substantially different from that found in normal tissue. For example, interstitial pressures are higher in solid tumors than in normal tissues and tumor microvasculature often has higher vascular permeability than normal microvasculature. Such factors should be accounted for by in-vitro models used to accurately evaluate potential drug delivery vehicles.